MLA

Bullitt, William C. (William Christian), 1891-1967. Photographs, people. Box 247, folder 62 - 64. undated. https://collections.library.yale.edu/catalog/10016013.

APA, 6th edition

Bullitt, William C. (William Christian), 1891-1967. (["Box 247, folder 62 - 64"])(undated)[Photographs, people]. https://collections.library.yale.edu/catalog/10016013.